Three-dimensional Time-stepping Finite-element Method Research Articles

Optimal design of a short primary double‐sided linear induction motor based on derived Quasi‐3D equivalent circuit model using an improved differential evolution

Due to its simple construction, the linear induction motor (LIM) provides a linear driving force without any intermediate motion translation system. LIMs are widely used in various industrial applications, including maglev rail transit and the national defense industry. However, LIMs are affected by the end effect and suffer from problems such as low efficiencies and low power factors. To make improvements, in this paper, an ensemble multi-objective optimal design method for a short primary double-sided linear induction motor (SP-DLIM) is proposed. First, a simplified Quasi-3D equivalent circuit model (ECM) for an SP-DLIM applicable to the model in this paper is derived. The 3-D transient finite element method and an experimental prototype are utilised to prove that the derived ECM is accurate enough to solve the SP-DLIM optimisation problem. Second, an ensemble multi-objective optimal design method of SP-DLIM is presented, with proposed design constraints and four different optimisation problems. Then, an improved differential evolutionary (IDE) algorithm is proposed to optimise the efficiency, power factor, and tooth weight of the motor. The three-dimensional time-stepping finite element method is utilised to verify the validity of the optimisation method. Further, a comparison of the results suggests that the IDE yields the best performance to those of other advanced heuristic algorithms.

Simplified Winding Arrangement for Integrated Multiturn Resolvers

Winding configuration is a crucial factor that highly affects the accuracy of resolvers. A nonoptimal winding could also make the manufacturing process complicated and costly inefficient. In this article, an approach to determine the optimal winding configuration for the resolvers is proposed. This method is applicable for both wound rotor (WR) and variable reluctance (VR) resolvers, and significantly simplifies the winding configuration of resolvers with different pole pairs and teeth numbers. Based on the proposed approach, the winding configuration of multiturn resolvers, which are generally more complicated than single-turn resolvers, is simplified for WR and VR type resolver with different number of stator teeth. In this approach, the reliability of the sensor is also considered. The proposed winding facilitates the manufacturing process and decreases the production costs for the multiturn resolver. The three-dimensional time-stepping finite-element method is used to confirm the correctness of the analysis. Finally, a prototype of the sensor is built and tested to verify the validity of the proposed winding approach. The measured value of the average of absolute position error for 1X/5X resolver is 0.197°/0.081°, and the maximum position error is 0.716°/0.212°.

Design and Optimization of a Multi-Turn Variable Reluctance Resolver

Multi-turn resolvers are supposed to be used in high accuracy industrial applications where both the high resolution and the absolute measurement are needed. The existed multi-turn resolvers are wound-rotor (WR) resolvers, while the variable reluctance (VR) resolvers are expected to be more cost efficient than WR resolvers, because they have a simple and solid rotor that makes them independent of using the rotary transformer. In this paper, a multi-turn VR resolver is proposed for such applications. Then, the proposed structure is optimized to decrease the ferromagnetic material’s volume and improve the performance of the sensor under mechanical faults. The studied mechanical faults include run out, static, dynamic, and mixed eccentricities that are studied independently and simultaneously. The analysis is done using three-dimensional time-stepping finite-element method (3-D TSFEM), and the optimal structure is experimentally built to validate the success of the design and optimizations.

Improved Winding Proposal for Wound Rotor Resolver Using Genetic Algorithm and Winding Function Approach

Among position sensors, resolvers are superior from reliability point of view. However, obtaining lower output voltage harmonics and simple manufacturing process is a challenge in the design and optimization of resolvers. In this paper, a metaheuristic optimization algorithm is used to minimize total harmonic distortion of the output signals, and consequently the estimated position error in concentrated coil wound field resolvers. Meanwhile, to minimize total coil numbers, manufacturing costs, and complexity of the winding process, modified objective function and constraints are proposed. In this way, a modified winding function method is employed for performance analysis of the axial flux resolver. Then, the merits of the optimized winding configuration with respect to fractional slot concentrated windings are shown. The results of the proposed configurations are verified with a three-dimensional time-stepping finite-element method. Finally, the prototype of the studied axial flux resolver is constructed and tested. Good agreement is obtained between simulation and experimental results, confirming the effectiveness of the optimization process.

Design, Analysis, and Prototyping of a New Wound-Rotor Axial Flux Brushless Resolver

Resolvers are electromagnetic position sensors that are widely used in industrial applications. In this study, a new axial flux brushless resolver (AFBR) with a wound rotor is introduced. In the proposed resolver, the core of the rotary transformer (RT) is omitted, and an innovative design is used to supply the excitation winding of the resolver. The proposed resolver can be built with smaller dimensions, and its thermal stability and mechanical strength are increased compared with conventional AFBRs. The performance of the proposed structure is simulated and optimized by using a three-dimensional time-stepping finite element method. The effect of the leakage flux of the RT on the excitation and signal windings is also discussed for both the proposed and conventional structures. A prototype based on the optimized topology is constructed and tested. Good agreement is obtained between the simulation and experimental results, validating the success of the proposed resolver.

Twelve‐slot two‐saliency variable reluctance resolver with non‐overlapping signal windings and axial flux excitation

In this study, a new 12-slot two-saliency variable reluctance (VR) resolver with simple non-overlapping windings is proposed. The excitation winding in the proposed resolver is replaced with one axial coil that is perpendicular to the signal windings. Both distributed and non-overlapping concentric windings with uniform coil turns are used. The rotor has two upper and lower saliencies located in front of each other. The shape and width of each saliency are determined based on the optimisation. Compared with conventional 12-slot VR resolvers, the proposed resolver has a simpler rotor structure and the advantages of two-saliency resolvers against eccentricity, absolute output position, and higher accuracy. The operation principle of the proposed resolver is analytically shown. Then, a three-dimensional time-stepping finite-element method (FEM) is used for the design, analysis, and optimisation of the proposed sensor. After optimisation, a prototype of the most accurate resolver is built. The good agreement obtained between the FEM and the practical results verifies the design and optimisation process.

Design oriented technique for mitigating position error due to shaft run‐out in sinusoidal‐rotor variable reluctance resolvers

Variable reluctance (VR) resolvers have some distinguish features over wounded rotor resolvers that make them suitable for industrial applications. Among different types of VR resolvers, sinusoidal-rotor resolvers are preferred due to simple structure and high performance under eccentricities. However, their accuracy is affected by inevitable run-out error. As they work based on sinusoidal variation of coupling area between stator and rotor and under run-out error the coupling area is impaired. Hence, in this study, a new disk shape configuration is proposed for sinusoidal-rotor resolver that is robust against run-out error. Geometrical dimensions are calculated based on optimisations to achieve more accuracy. Three-dimensional time-stepping finite-element method is used to show the preference of the proposed resolver. Finally, prototypes of both conventional and proposed sensors are built and tested. Experimental results verify the success of the proposed structure.

Optimization Design and Performance Analysis of a PM Brushless Rotor Claw Pole Motor with FEM

A new type of permanent magnet (PM) brushless claw pole motor (CPM) with soft magnetic composite (SMC) core is designed and analyzed in this paper. The PMs are mounted on the claw pole surface, and the three-phase stator windings are fed by variable-frequency three-phase AC currents. The advantages of the proposed CPM are that the slip rings on the rotor are cast off and it can achieve the efficiency improvement and higher power density. The effects of the claw-pole structure parameters, the air-gap length, and the PM thinner parameter of the proposed CPM on the output torque are investigated by using three-dimensional time-stepping finite element method (3D TS-FEM). The optimal rotor structure of the proposed CPM is obtained by using the response surface methodology (RSM) and the particle swarm optimization (PSO) method and the comparison of full-load performances of the proposed CPM with different material cores (SMC and silicon steel) is analyzed.

Performance Comparative Analysis of Flux-Modulated PM Machine with Two Topologies for Low-Speed Drive

Two types of flux-modulated (FM) PM machines are presented and analyzed quantitatively in this paper. Both of the two FM PM machines have the new topology structures which are differ from those of the traditional machine. In the design, the concentrated stator windings are built to reduce the end length, therefore to reduce copper losses and improve efficiency. Special iron pieces in the air-gap are used to modulate the magnetic field. According to different flux modulation form, the two proposed FM PM machines are classified as axial-flux-modulated machine (AFMM) and hybrid-flux-modulated machine (HFMM) respectively. This paper focuses on the performance comparative analysis of the two proposed FM PM machines by using three-dimensional time-stepping finite element method (3D TS-FEM). The flux distribution, electromotive force (EMF) waveforms, air-gap flux density, output torque, core losses and efficiency of the two proposed machines have been investigated.

A novel concept for derating of transformer under unbalance voltage in the presence of non linear load by 3-D finite element method

Unbalanced supply voltage and non-linear loads have become significant consideration in the designing transformers. This condition results in devastating effects such as high loss, early damage of insulation and premature failure of the transformers. For proper operation of transformers, capacity of transformer should be reduced. This paper presents a novel concept for mixed derating of distribution transformers under unbalance supply voltage in the presence of harmonic load conditions. The three-dimensional time stepping finite element method (TSFEM) based on Ansoft Maxwell is utilized as an instrument for calculation of losses and viewing magnetic flux density on core and windings of the distribution transformers. The results of simulation show that IEEE standard is a conservative method for transformer derating under unbalance voltage in the presence of high total harmonic distortion load current and TSFEM is a convenient and more precise method for transformer derating in this condition.

Analytical estimation of short circuit axial and radial forces on power transformers windings

In this study, an analytical method is proposed to calculate exerted axial and radial forces on the high and low voltage (LV) windings in core type power transformers. Hence, an analytical modelling approach is proposed to compute short circuit currents in the transient mode and steady state. The proposed model includes non-linear characteristics of the core materials, eddy currents effects, symmetrical and asymmetrical hysteresis loops of the used laminates. Then, exerted axial and radial forces on the high and LV windings are analytically computed in the transient mode and steady state. In order to certify obtained analytical results, the two-dimensional (2D) time stepping finite element method (TSFEM) is utilised to determine aforementioned forces. In this modelling approach, the geometrical, electrical and magnetic characteristics of the core type transformer under short circuit fault are taken into account. Furthermore, three-dimensional TSFEM is employed to verify the analytical and 2D TSFEMs results.

Investigation of characteristics of a single‐phase axial flux induction motor using three‐dimensional finite element method and d − q model

The aim of this study is to find out the performance characteristics of single-phase axial flux induction motors. In this study, three-dimensional time-stepping finite-element method is employed to analyse electromagnetic fields. Both eddy current and saturation effects are considered in the simulation. Since this transient solution is a computationally expensive method, a mathematical model based on d−q-axis theory is presented in this study. Then, the motor's electrical parameters, whose values are requested in the d−q model, are calculated using the analytical method and the DC-charge test of the built motor. The comparison between experimental and simulation results verifies the success of simulation.